The silver halide emulsion used for the direct positive silver halide photographic light-sensitive material according to the present invention is fogged in advance, and a solarization or a Herschel effect is utilized to break fogging nuclei by exposure, whereby a positive image is formed. The direct positive light-sensitive material can include a photographic light-sensitive material having a high sensitivity, in which a desensitizing dye is used, as shown in JP-B-50-3938 (the term "JP-B" as used herein means an examined Japanese patent publication) and JP-B-50-3937, and a light-sensitive material for daylight which can be handled in the daylight, as shown in JP-A-62-234156 (the term "JP-A" as used herein means an unexamined Japanese patent application) and JP-A-61-251843. The present invention relates to the silver halide emulsion used for these light-sensitive materials.
Usually, a direct positive type light-sensitive material is fogged with a reducing agent after the formation of the grains so that a reduced Ag nucleus is formed on the surface thereof to the extent that optical bleaching is possible. Obtaining the performance of high sensitivity and high contrast requires suppressing the degree of fogging and equalizing fogging among the grains. However, suppressing the degree of fogging to increase sensitivity makes it difficult to increase Dmax and softens gradation.
Suppressing the degree of fogging in order to suppress Dmin may result in a Dmax which is not sufficiently increased and a gradation which is liable to become soft.
Further, in a direct positive light-sensitive material for photographing, since it is required to increase sensitivity, the degree of fogging by a reducing agent can not be strengthened and, therefore, the resulting Ag nuclei are fine and unstable.
Meanwhile, in a direct positive light-sensitive material for daylight, the need for a decrease in sensitivity requires an intensification of the degree of fogging with a reducing agent and, therefore, the resulting Ag nuclei are not easily bleached by exposure and the Dmin is liable to increase.
It is proposed in JP-B-50-3978 to use a gold compound to increase stability of the Ag nuclei. However, even the use of a gold compound does not overcome the fact that the Ag nuclei remain insufficiently stable and Dmin is liable to increase.
Further, the development processing of the direct positive light-sensitive material has been carried out by a lith development (for example, HS-5 (developer) manufactured by Fuji Photo Film Co., Ltd.). In recent years, however, the trend for a processing system has been changed. That is, a rapid processing aptitude such as an RAS (a rapid access) processing and Hybrid processing (for example, Grandex manufactured by Fuji Photo Film Co. and Ultratec manufactured by Eastman Kodak Co., Ltd.) have been required. Thus, it is desired to achieve excellent performance with respect to Dmax, Dmin and high contrast as close as possible to those achieved with the lith processing.